Francisco J. Ayala, in full Francisco José Ayala (born March 12, 1934, Madrid, Spain), Spanish-born American evolutionary geneticist and molecular biologist best known for expounding the philosophical perspective that Darwinism and religious faith are compatible.

Ayala was raised in Madrid by his parents, Francisco and Soledad Ayala. He received a B.S. in physics from the University of Madrid in 1955. Between 1955 and 1960, he studied theology at the Pontifical Faculty of San Esteban in Salamanca, where he was ordained a priest in the Dominican order in 1960. He left the priesthood the same year.

In the 1970s Ayala investigated the process of genetic variation and natural selection at the molecular level. Later, he made significant contributions to public health through his research into the population structure, mode of reproduction, and evolution of parasitic protozoans.

Throughout his career, Ayala defended the teaching of evolution in public schools in the United States, and his efforts served to strengthen evolutionary theory. He served as an expert witness in McLean v. Arkansas Board of Education (1981), which overturned a state law that required the teaching of creationism alongside evolution in science classes. In 1984 and again in 1999, he was the principal author of Science and Creationism: A View from the National Academy of Sciences. In Darwin’s Gift to Science and Religion (2007), he argued that creationist beliefs run counter to theological concepts. For example, orthodox Christian beliefs posit the existence of an omnipotent, benevolentCreator despite the fact that the world is filled with predators, diseases, and other so-called “evils.” He notes that attributing these defects to an “intelligent designer” calls into question the Creator’s omnipotence and benevolence. However, by attributing these defects to the trial and error process of natural selection, the Creator is absolved of the responsibility of evil in the world.